In general, inkjet printing machines or printers include at least one printhead that ejects drops or jets of liquid ink onto the surface of media. An inkjet printer employs inks in which pigments or other colorants are suspended in a carrier or are in solution with a solvent. Once the ink is ejected onto media by a printhead, the carrier is solidified or the solvent is evaporated to stabilize the ink image on the media surface. The ejection of liquid ink directly onto media tends to soak into porous media, such as paper, and change the physical properties of the media. Particularly with aqueous inkjet printing systems, water from the aqueous ink swells the cellulose fibers of the media and elongates the media in areas where an image is formed, but not in non-imaged areas. A moisture gradient is developed in the media due to these localized differences in moisture content and this gradient may problematically lead to localized lack of sheet flatness, which is commonly called media cockle. Media cockle adversely affects image quality.
Attempts have been made to reduce media cockle in previous printing systems. For example, printing systems utilizing web-fed media often apply a tension to the media to help elongate the dry areas to match the elongation of the wet areas. However, such media tension methods cannot be implemented in printing systems that utilize cut-sheet media due to the relatively short length of cut-sheet media compared to webs of media. Cut-sheet media printing systems often rely on a drying system that directs electromagnetic radiation or convection air to the surface of the media. These drying systems may lower the moisture content of the entire sheet of media, but they fail to address moisture gradients effectively since the gradients are caused by localized variations in moisture content attributable to varying amounts of aqueous ink ejected on the media at various locations. Printer configurations that reduce such media cockle are desirable.